1. Field of the Invention
The present invention relates to low-profile keyboard input devices preferably used in notebook personal computers and the like.
2. Description of the Related Art
Hitherto, personal computers such as notebook computers to be used as portable terminal devices have been improved regarding miniaturization and weight-reduction.
A typical configuration of a keyboard input device used in such a notebook personal computer is described below with reference to FIG. 8.
A metallic plate 21 is provided with a film substrate 22. The film substrate 22 is provided thereon with a plurality of conducting patterns 23, which are electrically conductive, each conducting pattern 23 having a pair of fixed contact parts 23a and 23b. The fixed contact parts 23a and 23b are disposed opposing each other across a gap 23c therebetween.
A plurality of hollow domed elastic spring members 24 of an elastically-deformable material such as rubber are provided covering the fixed contact parts 23a and 23b. Each elastic spring member 24 includes a mounting flange 24a formed at the bottom thereof. A plurality of air-passage grooves 24b having predetermined width and depth are formed at the bottom of the mounting flange 24a opposing the film substrate 22 and the conducting pattern 23.
The elastic spring members 24 are bonded by an adhesive 25 to the film substrate 22 including the conducting patterns 23.
Each of the hollow elastic spring members 24 is provided with a protrusion 24c downwardly protruding from the inner top thereof. The protrusion 24c includes a movable conductive-contact part 24d formed at the end thereof.
Each of the domed elastic spring members 24 is provided with a key-receiving part 24e upwardly protruding from the outer top thereof.
The key-receiving part 24e receives a key-top 26 brought into contact therewith at the inner surface 26a of the key-top 26. The key-top 26 moves vertically while supported by a lifting mechanism (not shown) mounted on the metallic plate 21.
Mounting holes (not shown) are formed in the metallic plate 21 for mounting the lifting mechanism (not shown). The metallic plate 21 is provided with a sealing sheet 27 for sealing the mounting holes, laminated on the bottom surface of the metallic plate 21.
A known keyboard thus arranged operates in a manner such that air in the hollow elastic spring members 24 is discharged by the deformation of the hollow domed elastic spring members 24 pressed by the key-tops 26 through the air-passage grooves 24b provided at the mounting flanges 24a, whereby the key-tops 26 can smoothly move vertically with a light touch, thereby providing superior feeling in the key operation.
By pressing each key-top 26, the movable contact part 24d comes in contact with the fixed contact parts 23a and 23b, whereby the pair of the fixed contact parts 23a and 23b are electrically connected to each other through the movable contact part 24d. 
Such known keyboard devices are mounted in notebook personal computers used as portable terminal devices. At present, the notebook personal computers are often used outdoors even in wet weather, therefore, the need for waterproof keyboard devices is increasing.
However, the known keyboard device has a problem when used outdoors in wet weather in that there is a risk of discoloration and corrosion of the fixed contact parts 23a and 23b by water droplets adhering on the film substrate 22 and the conducting patterns 23 penetrating into the hollow elastic spring members 24 through the air-passage grooves 24b of the mounting flanges 24a. The problem is that there is a risk of defective conduction between the pair of the fixed contact parts 23a and 23b and the movable contact part 24b in contact therewith, which is caused by the discoloration or corrosion of the fixed contact parts 23a and 23b. Also, there is a risk of disconnection of the conducting patterns 23 by corrosion when water droplets remain on the conducting patterns 23, a portion of which is disposed at the outside of the elastic spring members 24.
Accordingly, it is an object of the present invention to provide a waterproof keyboard device in which water droplets of rain or the like are prevented from penetrating into elastic spring members when the keyboard device is used outdoors in wet weather.
In accordance with an aspect of the present invention, a keyboard input device is provided which comprises a flexible film substrate; a conducting pattern provided on the film substrate, including a pair of fixed contact parts opposing each other; a hollow domed elastic spring member including a movable contact part provided on the ceiling thereof, the movable contact part being vertically movable; and a key-top for pressing the top of the elastic spring member. The elastic spring member is mounted on the film substrate so that the movable contact part is disposed over the pair of the fixed contact parts. An air-passage hole is provided in the ceiling having the movable contact part, the air-passage hole being formed in the vertically moving direction of the movable contact part. Also, air-passage grooves communicating with the air-passage hole are formed in a direction perpendicular to the axis of the air-passage hole, the air-passage grooves being provided at least in one of the positions in the key-top at a portion thereof to be in contact with the top of the elastic spring member and in the elastic spring member at the top thereof. With this arrangement, the air in the hollow elastic spring member is discharged, when the key-top is pressed to deform the elastic spring member, to the outside of the elastic spring member through the air-passage hole and the air-passage grooves.
The keyboard input device according to the present invention may be provided with an insulating overcoat, which is moisture-resistant and water-repellent, disposed on the film substrate including the conducting pattern with the pair of the fixed contact parts being exposed, and may be provided with the elastic spring member bonded to the overcoat by an adhesive.
In the keyboard input device according to the invention, the film substrate may be provided with a hole between the pair of the fixed contact parts which oppose each other across the hole therebetween.
According to another aspect of the present invention, a keyboard input device is provided which comprises a metallic plate; a flexible film substrate disposed on the metallic plate; a conducting pattern including a pair of fixed contact parts formed thereon opposing each other; a hollow domed elastic spring member including a movable contact part provided on the ceiling thereof, the movable contact part being vertically movable; and a key-top for depressing the top of the elastic spring member. A first hole is formed in the film substrate in the vicinity of the fixed contact parts, and an air-passage hole is formed in the metallic plate at a position in which the first hole is disposed, in the moving direction of the movable contact part. With this arrangement, the air in the hollow elastic spring member is discharged, when the key-top is pressed to deform the elastic spring member, to the lower part of the metallic plate through the first hole and the air-passage hole.
The keyboard input device according to the invention may be provided with an insulating overcoat, which is moisture-resistant and water-repellent, disposed on the film substrate including the conducting pattern with the pair of the fixed contact parts being exposed, and the elastic spring member is bonded to the overcoat by an adhesive.
In the keyboard input device according to the invention, the first hole in the film substrate may be disposed in a position flanked by the pair of the fixed contact parts.
In the keyboard input device according to the invention, the film substrate may be bonded to the metallic plate, and the first hole and the air-passage hole may be formed by punching in one operation.